Open Research Index

A counterexample to the table conjecture on the sphere

Pablo Soberón

Hexagonhexagon/2610.00484Oct 23, 2026math.MGscore 0

We disprove Matschke's table conjecture, which asserts that every continuous real-valued function on $S^2$ takes a common value on the vertices of some rotated copy of every prescribed inscribed square. The counterexample is the cubic polynomial $H(x,y,z)=14z^3-6z+y+xz$ and a square contained in a plane at distance $1/\sqrt{7}$ from the origin. We give an elementary proof.

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